Oceans and Seas Quiz
From the Mariana Trench to the Sargasso Sea: 15 questions on the water that covers most of our planet.
Which is the largest ocean on Earth?
Got a hunch? Pick the answer that feels right.
Pacific Ocean
The Pacific covers roughly 165 million square kilometres (63 million square miles), about a third of the planet's surface, and holds more water than all the other oceans combined.
Ferdinand Magellan named it Mar Pacífico, the peaceful sea, in 1520 after finding calm waters following a brutal passage around South America.
Which is the smallest of the world's oceans?
Got a hunch? Pick the answer that feels right.
Arctic Ocean
The Arctic Ocean covers only about 14 million square kilometres (5.4 million square miles) around the North Pole, making it the smallest and shallowest of the five oceans.
Much of the Arctic Ocean is covered by sea ice for most of the year, and the North Pole itself sits on floating ice rather than land.
Which strait connects the Mediterranean Sea to the Atlantic Ocean?
Got a hunch? Pick the answer that feels right.
Strait of Gibraltar
The Strait of Gibraltar separates Spain from Morocco and is only about 14 kilometres (9 miles) wide at its narrowest point, making it the Mediterranean's single gateway to the Atlantic.
The ancient Greeks called the headlands on either side the Pillars of Hercules, long regarded as the edge of the known world.
Which gulf between Iran and the Arabian Peninsula is reached through the Strait of Hormuz?
Got a hunch? Pick the answer that feels right.
Persian Gulf
The Persian Gulf lies between Iran and the Arabian Peninsula, and the narrow Strait of Hormuz at its mouth carries around a fifth of the world's oil shipments.
Many Arab countries call it the Arabian Gulf, and the naming dispute has caused diplomatic rows and even cancelled sporting events.
Which sea lies between Italy and Croatia?
Got a hunch? Pick the answer that feels right.
Adriatic Sea
The Adriatic Sea is the arm of the Mediterranean that separates the Italian peninsula from the Balkans, with Venice at its northern end and Croatia's island-studded coast on its eastern shore.
Venice's lagoon sits at the head of the Adriatic, and the city's historic tides and floods are driven by winds pushing water up the sea's length.
The Challenger Deep, the deepest known point in the oceans, lies in which trench?
Got a hunch? Pick the answer that feels right.
Mariana Trench
The Challenger Deep in the western Pacific's Mariana Trench reaches roughly 10,935 metres (35,876 feet) below sea level, so deep that Mount Everest could sit inside it with room to spare.
Film director James Cameron made a solo dive to the Challenger Deep in 2012, only the second crewed descent after Piccard and Walsh in 1960.
Which bay, bordered by India, Bangladesh, Myanmar and Sri Lanka, is the largest bay in the world?
Got a hunch? Pick the answer that feels right.
Bay of Bengal
The Bay of Bengal covers about 2.2 million square kilometres (840,000 square miles) in the north east of the Indian Ocean and receives the Ganges and Brahmaputra rivers.
The Bay of Fundy in Canada has the highest tides on Earth, with a range of up to 16 metres (53 feet).
Which sea lies between mainland Greece and Turkey?
Got a hunch? Pick the answer that feels right.
Aegean Sea
The Aegean Sea is the arm of the Mediterranean between Greece and Turkey, dotted with islands such as Crete, Rhodes, Santorini and Mykonos that shaped ancient Greek civilisation.
Legend says the sea is named after King Aegeus of Athens, who threw himself into it believing his son Theseus had died fighting the Minotaur.
The River Danube empties into which sea?
Got a hunch? Pick the answer that feels right.
Black Sea
The Danube flows about 2,850 kilometres (1,770 miles) from Germany's Black Forest through ten countries before spreading into a vast delta on Romania's Black Sea coast.
The Black Sea connects to the Mediterranean only through the narrow Bosporus and Dardanelles straits, which run through Turkey past Istanbul.
Which ocean completely surrounds Antarctica?
Got a hunch? Pick the answer that feels right.
Southern Ocean
The Southern Ocean is the ring of water encircling Antarctica, generally defined as everything south of 60 degrees south, and it is the youngest ocean to be widely recognised.
The Antarctic Circumpolar Current flows through it unobstructed by land, carrying more water than any other current on Earth.
Which strait separates Russia from Alaska?
Got a hunch? Pick the answer that feels right.
Bering Strait
The Bering Strait is only about 82 kilometres (51 miles) wide at its narrowest and separates the easternmost tip of Asia from the westernmost point of mainland North America.
The International Date Line runs down the strait, so the Diomede Islands in its middle are almost a full day apart despite being just 4 kilometres (2.5 miles) apart.
Which sea is the only one in the world with no coastline?
Got a hunch? Pick the answer that feels right.
Sargasso Sea
The Sargasso Sea sits in the middle of the North Atlantic and is bounded entirely by ocean currents rather than land, with the Gulf Stream forming its western edge.
It is named after the floating sargassum seaweed that drifts on its surface, and it is the spawning ground of both European and American eels.
The Caspian Sea is often called the world's largest lake. Which of these countries has a Caspian coastline?
Got a hunch? Pick the answer that feels right.
Iran
The Caspian Sea is bordered by Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan, and its southern shore is entirely Iranian, home to the ports of Bandar-e Anzali and Nowshahr.
At roughly 371,000 square kilometres (143,000 square miles) the Caspian is bigger than Germany, yet it is landlocked and its water is only about a third as salty as the ocean.
Which island nation sits directly on top of the Mid-Atlantic Ridge?
Got a hunch? Pick the answer that feels right.
Iceland
Iceland straddles the boundary between the North American and Eurasian plates, which is why the Mid-Atlantic Ridge rises above sea level there and the island is so volcanically active.
At Thingvellir National Park visitors can walk through a rift valley where the two plates are pulling apart at about 2 centimetres (0.8 inches) a year.
Which trench contains the deepest point in the Atlantic Ocean?
Got a hunch? Pick the answer that feels right.
Puerto Rico Trench
The Puerto Rico Trench's Milwaukee Deep reaches about 8,376 metres (27,480 feet), the deepest spot in the Atlantic, as confirmed by Victor Vescovo's crewed descent in 2018.
The trench is named after the USS Milwaukee, which first sounded its depths in 1939, and it marks where the North American plate meets the Caribbean plate.
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All Geography quizzes →About the Oceans and Seas Quiz
Water covers about 71 percent of the Earth, and the Pacific Ocean alone is bigger than every landmass on the planet combined. The deepest point anyone has measured, the Challenger Deep, sits nearly 11 kilometres (6.8 miles) below the waves, deeper than Everest is tall. Meanwhile the Sargasso Sea has no coastline at all, and the Bay of Bengal is the largest bay on the planet.
These 15 questions cover the five oceans, the famous seas of Europe and the Middle East, the straits that join them, and a few deeper cuts like the Puerto Rico Trench and the Mid-Atlantic Ridge. It suits anyone who loved the globe in school, armchair sailors, and pub quiz regulars who want a confident run through the blue bits of the map.
You will find 15 multiple choice questions here, each with four options. Difficulty: Medium. Most people finish in about 6 minutes, and every answer comes with a short explanation and one extra fact worth keeping.
How to play
Read the question and pick one of the four answers. The correct answer is revealed straight away with a short explanation, then press Next question to keep going. At the end you get your score out of 15 and a full review of your round. Play again any time and the questions arrive in a fresh order. There is no timer and no account.
Good to know before you play
Which is the largest ocean?
The Pacific Ocean is by far the largest, covering roughly 165 million square kilometres (63 million square miles), about a third of the Earth's surface.
How many oceans are there?
Most geographers now count five: the Pacific, Atlantic, Indian, Southern and Arctic. The Southern Ocean around Antarctica was formally recognised by many bodies in the 2000s.
What is the deepest point in the ocean?
The Challenger Deep in the Mariana Trench, roughly 10,935 metres (35,876 feet) below sea level in the western Pacific.
Answer key: all 15 questions with explanations
- Which is the largest ocean on Earth?
Pacific Ocean The Pacific covers roughly 165 million square kilometres (63 million square miles), about a third of the planet's surface, and holds more water than all the other oceans combined. Ferdinand Magellan named it Mar Pacífico, the peaceful sea, in 1520 after finding calm waters following a brutal passage around South America. - Which is the smallest of the world's oceans?
Arctic Ocean The Arctic Ocean covers only about 14 million square kilometres (5.4 million square miles) around the North Pole, making it the smallest and shallowest of the five oceans. Much of the Arctic Ocean is covered by sea ice for most of the year, and the North Pole itself sits on floating ice rather than land. - Which strait connects the Mediterranean Sea to the Atlantic Ocean?
Strait of Gibraltar The Strait of Gibraltar separates Spain from Morocco and is only about 14 kilometres (9 miles) wide at its narrowest point, making it the Mediterranean's single gateway to the Atlantic. The ancient Greeks called the headlands on either side the Pillars of Hercules, long regarded as the edge of the known world. - Which gulf between Iran and the Arabian Peninsula is reached through the Strait of Hormuz?
Persian Gulf The Persian Gulf lies between Iran and the Arabian Peninsula, and the narrow Strait of Hormuz at its mouth carries around a fifth of the world's oil shipments. Many Arab countries call it the Arabian Gulf, and the naming dispute has caused diplomatic rows and even cancelled sporting events. - Which sea lies between Italy and Croatia?
Adriatic Sea The Adriatic Sea is the arm of the Mediterranean that separates the Italian peninsula from the Balkans, with Venice at its northern end and Croatia's island-studded coast on its eastern shore. Venice's lagoon sits at the head of the Adriatic, and the city's historic tides and floods are driven by winds pushing water up the sea's length. - The Challenger Deep, the deepest known point in the oceans, lies in which trench?
Mariana Trench The Challenger Deep in the western Pacific's Mariana Trench reaches roughly 10,935 metres (35,876 feet) below sea level, so deep that Mount Everest could sit inside it with room to spare. Film director James Cameron made a solo dive to the Challenger Deep in 2012, only the second crewed descent after Piccard and Walsh in 1960. - Which bay, bordered by India, Bangladesh, Myanmar and Sri Lanka, is the largest bay in the world?
Bay of Bengal The Bay of Bengal covers about 2.2 million square kilometres (840,000 square miles) in the north east of the Indian Ocean and receives the Ganges and Brahmaputra rivers. The Bay of Fundy in Canada has the highest tides on Earth, with a range of up to 16 metres (53 feet). - Which sea lies between mainland Greece and Turkey?
Aegean Sea The Aegean Sea is the arm of the Mediterranean between Greece and Turkey, dotted with islands such as Crete, Rhodes, Santorini and Mykonos that shaped ancient Greek civilisation. Legend says the sea is named after King Aegeus of Athens, who threw himself into it believing his son Theseus had died fighting the Minotaur. - The River Danube empties into which sea?
Black Sea The Danube flows about 2,850 kilometres (1,770 miles) from Germany's Black Forest through ten countries before spreading into a vast delta on Romania's Black Sea coast. The Black Sea connects to the Mediterranean only through the narrow Bosporus and Dardanelles straits, which run through Turkey past Istanbul. - Which ocean completely surrounds Antarctica?
Southern Ocean The Southern Ocean is the ring of water encircling Antarctica, generally defined as everything south of 60 degrees south, and it is the youngest ocean to be widely recognised. The Antarctic Circumpolar Current flows through it unobstructed by land, carrying more water than any other current on Earth. - Which strait separates Russia from Alaska?
Bering Strait The Bering Strait is only about 82 kilometres (51 miles) wide at its narrowest and separates the easternmost tip of Asia from the westernmost point of mainland North America. The International Date Line runs down the strait, so the Diomede Islands in its middle are almost a full day apart despite being just 4 kilometres (2.5 miles) apart. - Which sea is the only one in the world with no coastline?
Sargasso Sea The Sargasso Sea sits in the middle of the North Atlantic and is bounded entirely by ocean currents rather than land, with the Gulf Stream forming its western edge. It is named after the floating sargassum seaweed that drifts on its surface, and it is the spawning ground of both European and American eels. - The Caspian Sea is often called the world's largest lake. Which of these countries has a Caspian coastline?
Iran The Caspian Sea is bordered by Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan, and its southern shore is entirely Iranian, home to the ports of Bandar-e Anzali and Nowshahr. At roughly 371,000 square kilometres (143,000 square miles) the Caspian is bigger than Germany, yet it is landlocked and its water is only about a third as salty as the ocean. - Which island nation sits directly on top of the Mid-Atlantic Ridge?
Iceland Iceland straddles the boundary between the North American and Eurasian plates, which is why the Mid-Atlantic Ridge rises above sea level there and the island is so volcanically active. At Thingvellir National Park visitors can walk through a rift valley where the two plates are pulling apart at about 2 centimetres (0.8 inches) a year. - Which trench contains the deepest point in the Atlantic Ocean?
Puerto Rico Trench The Puerto Rico Trench's Milwaukee Deep reaches about 8,376 metres (27,480 feet), the deepest spot in the Atlantic, as confirmed by Victor Vescovo's crewed descent in 2018. The trench is named after the USS Milwaukee, which first sounded its depths in 1939, and it marks where the North American plate meets the Caribbean plate.
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